did you read chapter 1? it clearly says it was 2 years since she left the industry after her mother dies, then a few days later, 'affair' being exposed, people then call it retribution that her 'secret is exposed' because she didn't even attend her mothers funeral(which she apparently didn't even know had happened, so it was hardly over night,the 2 months before is referring to when she got a hand of the video of that guy suppressing the news of her mother's death(which is why I say her mother died before, why else would supressing the news of her mothers death be so important), which is the time between her attempted suicide to when she went to join that opposing company, she losing weight in a short period of time is not a unheard of "phenomenon" . binge eating and high stress will change your weight quite drastically, however losing that weight isn't necessarily that hard. because once stress is relieved or depression is relieved, binge eating stops and you start exercising it can go down again quite rapidly.
there is a difference in what made you big in the first place as well.
binge eating - stress- depression - possibly medication that can have side effects of water retention etc, anti depressants commonly have this effect, illness|disease/disorders etc.
you simply being big because you eat alot despite no actual conditions above being met will take quite a bit more to get rid of(assuming you are not incurable of said illnesses or rely on the medication to live)
example, you can get something called moon face from certain anti depressants amongst other medications, this can make a person who is just slightly overweight to look extremely overweight, but this moon face side effect disappears rapidly after you stop using the medication, but it will also account for a fair bit of weight.